The present invention relates to a valve operating apparatus for an internal combustion engine with a plurality of cylinder groups which variably controls the valve lift and open duration of engine valves depending on engine operating conditions, and particularly to the valve operating apparatus which can reduce a difference between valve lift characteristics of the engine valves of the respective cylinder groups.
Japanese Patent Application First Publication No. 2003-176707 discloses a valve operating apparatus for a V-type internal combustion engine having two groups of cylinders. The valve operating apparatus of this conventional art includes intake valves which are slidably disposed within cylinders in cylinder heads of right and left banks, two drive shafts which are supported on the respective cylinder heads and have drive cams integrally formed with the drive shafts on the outer circumferential periphery, swing cams swingably supported on the respective drive shafts, valve lifters which are contacted with the swing cams and actuate the respective intake valves, and a variable operation mechanism for variably controlling the valve lift and open duration of the respective intake valves. The drive shafts on the right and left banks are operated to rotate in the same direction by torque from a crankshaft of the engine.
The variable operation mechanism of the valve operating apparatus of the above conventional art includes a multi-link motion transmission mechanism for converting the torque of the drive cams to a swing motion of the swing cams and a control mechanism which controls the motion transmission mechanism depending on the engine operating condition so as to vary contact portions of the cam surfaces of the swing cams which are contacted with the corresponding valve lifters to thereby adjust the valve lift amount and open duration of the respective intake valves. A variable phase control mechanism is provided for controlling an offset in valve lift phase between the right bank side and the left bank side.